A comparison of electrochemical degradation of phenol on boron doped diamond and lead dioxide anodes

This work compares two electrode materials used to mineralize phenol contained in waste waters. Two disks covered with either boron doped diamond (BDD) or PbO2 were used as anodes in a one compartment flow cell under the same hydrodynamic conditions. Efficiencies of galvanostatic electrolyses are compared on the basis of measurements of Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD). Galvanostatic electrolyses were monitored by analysis of phenol and of its oxidation derivatives to evaluate the operating time needed for complete elimination of toxic aromatics. The experimental current efficiency is close to the theoretical value for the BDD electrode. Other parameters being equal, phenol species disappeared at the same rate using the two electrode materials but the BDD anode showed better efficiency to eliminate TOC and COD. Moreover, during the electrolysis less intermediates are formed with BDD compared to PbO2 whatever the current density. A comparison of energy consumption is given based on the criterion of 99% removal of aromatic compounds

Photocatalytic degradation of Basic Red 46 and Basic Yellow 28 in single and binary mixture by UV/TiO2/periodate system

PubMedID: 18995958The present study deals with the investigation of photocatalytic degradation and mineralization of C.I. Basic Red 46 (BR46) and C.I. Basic Yellow 28 (BY28) dyes in single and binary solutions as a function of periodate ion concentration (IO4-), irradiation time, initial pH and initial dye concentrations. First order derivative spectrophotometric method was used for to simultaneous analysis of BY28 and BR46 in binary mixtures. Langmuir-Hinshelwood kinetic model was applied to experimental data and apparent reaction rate constant values were calculated. The apparent degradation rate constant values of BR46 were higher than those of BY28 for all experiments in single dye solutions. On the other hand, the significant reductions were observed for the apparent degradation rate constant values of the BR46 in the presence of BY28 in binary solutions whereas TOC removal efficiency slightly enhanced in binary system. The highest TOC removal efficiency was obtained at pH 3.0 by adding 5 mM periodate ion in to the solution in the presence of 1 g/L TiO2 for both dye solutions. After 3 h illumination, 68, 76 and 75% mineralization were found for 100 mg/L BY28, 100 mg/L BR46 and 50 + 50 mg/L mixed solutions, respectively. © 2008 Elsevier B.V. All rights reserved.Firat University Scientific Research Projects Management UnitThis work was supported by the Mersin University Scientific Research Project Unit (Me.U.-BAB-FEF KB (BG) 2005-1)

Oxidative degradations of reactive blue 4 dye by different advanced oxidation methods

PubMedID: 19269087The degradations of an anthraquinone dye, the reactive blue 4 (RB4), were studied by wet air oxidation (WAO), wet peroxide oxidation (WPO), photocatalytic oxidation, and electro-Fenton (EF) advanced oxidation. The RB4 oxidation was evaluated by the decrease in total organic carbon (TOC) content and concentration. The most efficient method for mineralization of RB4 was WPO, but in all methods TOC removal efficiency was above 75% after 60 min of treatment. © 2009 Elsevier B.V. All rights reserved.Scientific Research Foundation of Beijing Normal UniversityThis work was supported by the Mersin University Scientific Research Foundation. We wish to thank Prof Ayla Özer and master student Muhammet Demirel for their supports

Effect of insulation on the energy and exergy performances in Diffusion Absorption Refrigeration (DAR) systems

In this study, the effect of insulation on the energy and exergy performances of DAR systems was investigated. A DAR system with the insulated generator-bubble pump (DAR1) was compared with a DAR system having the insulated generator-bubble pump, solution heat exchanger and partial-insulated rectifier (DAR2) experimentally and both components of the DAR1 and the DAR2 systems were insulated by rock wool. In the analyses, the energy losses rejected to ambient from rectifier and condenser, the energy gain (heat gain) by evaporator and also energy performance and exergy performance were calculated. While energy and exergy performances of DAR1 system were determined as 0.35 and 0.095, respectively, the performance values of DAR2 system were calculated as 0.44 and 0.115. As a consequence, the insulation of solution heat exchanger and the insulation of a part of rectifier in the DAR system increased the energy performance by 26% and the exergy performance by 21%. © 2014 Elsevier B.V. All rights reserved

Indirect electrochemical treatment of bisphenol A in water via electrochemically generated Fenton's reagent

PubMedID: 12953886Bisphenol A (BPA) has been treated with electrochemically generated Fenton's reagent in aqueous medium. Hydroxyl radicals that were formed in Fenton's reagent reacted with the organic substrate producing two different isomers of monohydroxylated product and, upon successive hydroxylation, mainly one dihydroxylated product. Further hydroxylation first degraded one of the aromatic rings, and the side chain thus formed was then cleaved off the other aromatic ring. The second aromatic ring was also degraded upon successive hydroxylations. Small saturated and unsaturated aliphatic acids were the last products prior to mineralization. It was found that use of cuprous/ cupric ion pair resulted a faster conversion of BPA and faster mineralization when compared using ferrous/ferric ions, but this happened at the expence of excess electrical charge utilized for an equivalent conversion or mineralization. Degradation by using ferrous/ferric ions was more efficient than cuprous/cupric ions case in terms of total mineralization versus charge utilized, and a mineralization of 82% had been achieved by applying 107.8 mF of charge to a 0.7 mM BPA solution of 0.200 dm3. The rate constant of the monohydroxylation of BPA in the presence of ferrous/ ferric ions had been determined as 1.0 × 1010 M-1 s-1 where BPA and salicylic acid competitively reacted with hydroxyl radicals in aqueous medium with the initial concentrations of Fe2+, BPA, and SA of 1.0, 0.5, and 0.5 mM, respectively. In a similar experiment where the initial concentrations of Cu2+, BPA, and SA were 1.0, 0.5, and 0.5 mM, respectively, the corresponding rate constant was determined to be the same as the rate constant obtained for Fe2+ (i.e., 1.0 × 1010 M-1 s-1). While the use of Cu2+ cannot be advised for processing BPA and similar substrates by using the electro-Fenton technique for both technical and economical reasons, the use of [Fe2+]/[BPA]0 values in the range 3-4 will be sufficient to achieve an efficient mineralization of BPA and similar substrates by the electro-Fenton process in aqueous medium

Optimization of solvent extraction process of some Turkish coals using response surface methodology and production of ash-free coal

In order to produce ash-free coal (AFC) from three Turkish coals, solvent extraction of coals using 1-methylnaphthalene (1-MN) at different temperatures were conducted. The extraction yield of coals was found dependent on coal, temperature, and solvent type. When there was usage of 1-MN as solvent, the extraction yield was low. However, on addition of N-methyl-2-pyryrolidone (NMP) or quinoline (QN) into 1-MN, the extraction yield increased. Following the extractions, we obtained AFC with less than 0.65% ash content for the three coals used in this study. The response surface methodology (RSM) was employed to investigate the solvent extraction conditions. The factors investigated were extraction temperature and additional polar solvent ratio. The obtained results demonstrated that either excess amount of polar solvent into 1-MN should be added at low temperatures or extraction should be done at high temperatures using less polar solvent to obtain an increase in extraction efficiency. The sensitivity and validity of results obtained by RSM were confirmed through validation experiments. The results of validation experiments showed a good agreement between the experimental and predicted values (relative error <1.2) and that indicated the robustness of the models. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd. © 2016 Curtin University of Technology and John Wiley & Sons, Ltd

Degradations of model compounds representing some phenolics in olive mill wastewater via electro-Fenton and photoelectro-Fenton treatments

PubMedID: 21879543The electrochemical oxidation of vanillic acid, o-coumaric acid and protocatechuic acid, three representative toxic phenolics in olive mill wastewater, was studied using carbon felt cathode in the electro-Fenton system. Results obtained, in the presence or absence of UV support, were compared throughout the degradation processes up to mineralization. It was demonstrated that all three phenolic compounds reacted completely with hydroxyl radicals and degraded efficiently. It was shown in the photoelectro-Fenton process that the degradation and mineralization efficiency of the phenolic compounds were enhanced by the effect of UV light, especially at the later stages of the degradation processes. © 2011 Taylor & Francis

Direct liquefaction of high-sulfur coals: Effect of the catalyst, the solvent, and the mineral matter

Two low-rank coals with high sulfur contents (Gediz subbituminous coal: 7.6 wt % S:dry basis. Çayirhan lignite: 5.7 wt% S:dry basis.) were subjected to hydroliquefaction. Liquefaction conditions included dry or solvent mediated runs under pressurized hydrogen without added catalyst or with the impregnated catalyst precursor ammonium heptamolybdate (AHM). Gediz coal having higher sulfur content gave 90% conversion in the absence of catalyst and solvent. Maximum conversion (98%) and maximum oil + gas yield (70%) from this coal were obtained by impregnating AHM onto coal and carrying out liquefaction in H2/tetralin system at 450 °C for 30 min. Under the same conditions, Çayirhan lignite gave 85% conversion and 70.5% oil + gas yield. The superior hydrodesulfurization effect of impregnated AHM on the oil fraction when used in the absence of solvent (less than 0.1% S in lignite's oil and less than 1% S in subbituminous coal's oil following one-stage hydrogenation) is a promising finding of this work. AHM was found to be much more effective in liquefaction of Çayirhan lignite and this has been ascribed to the well-dispersion of AHM throughout this lignite's structure via a cation-exchange mechanism through oxygen functionalities. Strong evidence for the catalytic effect of clay minerals in coal structure on char-forming reactions during liquefaction was observed by making use of liquefaction reactions of demineralized coal samples. It was also observed that tetralin had a retarding effect on the condensation and subsequent cross-linking reactions

Influence of the addition of various ionic liquids on coal extraction with NMP

In this work, two Turkish coals were extracted with N-methyl-2-pyrrolidone (NMP) and NMP containing a small amount of ionic liquids (ILs) under reflux conditions at atmospheric pressure. The effects of coal type, ionic liquid type, ionic liquid-to-coal ratio, and ultrasonic interactions on extraction yield were investigated. The ILs used were: 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-buty-4- methylpyridinium chloride ([Bmp]Cl), 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), and 1-butyl-2,3-dimethylimidazolium chloride ([Bdmim]Cl). It was found that the extraction yield of coals using NMP/ILs varied with coal type, IL type and amount of IL. ILs were effective on the extraction of Afsin-Elbistan (AE) lignite, but not on the extraction of Üzülmez (UZ) coal. A significant increase in extraction yield for AE lignite was observed when a small amount of IL was added into NMP. It was determined that [Bmim]Cl was the most efficient IL used for the extraction of lignite compared to the others ILs used, and the extraction efficiency was found to increase by increasing the amount of ionic liquid added into NMP. © 2017 Elsevier Ltd114?M878The authors are grateful to the TUBITAK (Scientific and Technical Research Council of Turkey, Project Reference 114?M878) for the financial support

Efficient removal of insecticide "imidaclopride" from water by electrochemical advanced oxidation processes

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